.c1{
    background-color: gray;
    height: 800px;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    opacity:0.6;
}
.c2{
    background-color: white;
    height: 300px;
    width: 300px;
    position: fixed;
    left:50%;
    top:50%;
    margin: -150px;


}
.hide{
    display: none;
}